Pituitary Adenoma: A review of existing classification systems based on anatomic extension and invasion.

Pituitary adenomas are common, benign tumours, that can be classified in many ways including their functionality, size and anatomical extension. Historically, larger more invasive adenomas with extension into parasellar regions were deemd untreatable. However, with increasing operative sophistication, and more precise and effective radiation options; it is no longer the case, and therefore it becomes even more important for a comprehensive classification system for these tumours. Herein, the authors present an updated review on the available classification systems for large pituitary adenomas, based on their anatomic extension and invasion of adjacent anatomic structures.